It's possible to connect RS-232 peripheral to the RS-422 port available on Macintosh computers. Use RXD- as RXD, TXD- as TXD, Ground RXD+, Leave TXD+ unconnected, GPi as CD.
 (at the computer)
 (at the computer)
8 PIN MINI-DIN FEMALE at the computer.
| Pin | Name | Dir | Description | 
|---|---|---|---|
| 1 | HSKo |  | Output Handshake | 
| 2 | HSKi/CLK |  | Input Handshake or External Clock | 
| 3 | TXD- |  | Transmit Data (-) | 
| 4 | GND |  | Ground | 
| 5 | RXD- |  | Receive Data (-) | 
| 6 | TXD+ |  | Transmit Data (+) | 
| 7 | GPi |  | General Purpose Input | 
| 8 | RXD+ |  | Receive Data (+) | 
Note: Direction is DTE (Computer) relative DCE (Modem).
Note: GPi is connected to SCC Data Carrier Detect (or to Receive/Transmit Clock if the VIA1 SYNC signal is high). Not connected on the Macintosh Plus, Classic, Classic II, LC, LC II or IIsi.
| Contributor: | Joakim Ögren, Pierre Olivier, Ben Harris, Nathan Schmidt | 
| Source: | comp.sys.mac.comm FAQ Part 1 | 
| Apple Tech Info Library, Article ID: TECHINFO-0001699 | 
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  Document last modified: 2002-01-10